The primary goal is to obtain morphological data on the effects of malnutrition on the central nervous system of young rats and of infant humans. A systematic study will be made of the brain and spinal cord of rats, which have been reared on known nutritionally-deficient diets for different intervals during the prenatal and/or early postnatal life. A similar study will be made of littermate rats which have been subsequently reared on optimal diets; this is designed to determine the degree, if any, of the recovery from the malnutrition. These will be compared with the central nervous system of rats reared on an optimal diet. The microscopic anatomy of human infants, who have died from severe malnutrition (e.g., maramus) will also be examined. Methods: All the rats used in these experiments will be reared on known diets, standard procedures and controlled environmental conditions used by the Institute of Human Nutrition, Columbia University. The brains and spinal cords will be prepared for histological examination by established neuroanatomical, neuropathological and autoradiographic techniques. These methods selected are designed for obtaining (1) information related to time of origin of each cell type (autoradiography), (2) qualitative observations of several structures (e.g., Nissl substance, myelin and glia), and (3) quantitative data of the number of each cell type per unit volume in several regions.